Immunomodulation by gadolinium chloride-induced Kupffer cell phagocytosis blockade

Gadolinium chloride (GdCl3), a rare earth metal salt, depresses macrophage activity, and is commonly used to study the physiology of the reticuloendothelial system. In the present work, the effect of GdCl3-induced Kupffer cell blockade on the humoral immune response in mice to sheep red blood cells (SRBC) was investigated. Kupffer cell phagocytosis blockade was found to increase both the primary and secondary immune responses to SRBC. The primary immune response was significantly augmented in animals injected intravenously with GdCl3 2, 3 or 4 days before injection of the cellular antigen, but GdCl3 injected 7 days before the antigen did not modify the immune response. Increased secondary humoral immune responses were also observed. When GdCl3 was injected 2 days before the second dose of antigen, the numbers of both IgM and IgG-producing plaque forming cells were augmented. GdCl3 injected 2 days before the first dose of SRBC did not modify the humoral immune response. Earlier studies with Cr-51-labelled foreign red blood cells suggested that the augmentation of the humoral immune response in GdCl3-pretreated mice is a consequence of the spillover of the antigen from the liver into the spleen and other extrahepatic reticuloendothelial organs. (C) 1998 Elsevier Science S.A.